Dashboard Cards: Activity Card Foundation

[zwarm]

Parent #18210

This PR adds the foundational pieces for the Activity Card dashboard item. To keep this PR small it only includes behind the scenes work, no card is displayed.

Includes

• String and dimen resources
• Activity card layout and card items layout
• ActivityCard class structures (this will be further built out in later PRs)
• View holders and adapters (this will be further built out in later PRs)
• Updates to CardsAdapter
• Updates to MySIteCardAndItem
• Updates to CardsTracker and CardsShownTracker

Note: The remainder of the build out will take place in a separate PRs and will include builder and params, building out ActivityItem, tweaking the UI and displaying the card.

To test:
There is nothing to test in this PR, as this is all foundational work.

Regression Notes

1. Potential unintended areas of impact
   N/A

2. What I did to test those areas of impact (or what existing automated tests I relied on)
   N/A

3. What automated tests I added (or what prevented me from doing so)
   N/A

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress by scanning the QR code below to install the corresponding build.

	App Name	WordPress
	Flavor	Jalapeno
	Build Type	Debug
	Version	pr18270-a9e40b0
	Commit	a9e40b0
	Direct Download	wordpress-prototype-build-pr18270-a9e40b0.apk

Note: Google Login is not supported on these builds.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack by scanning the QR code below to install the corresponding build.

	App Name	Jetpack
	Flavor	Jalapeno
	Build Type	Debug
	Version	pr18270-a9e40b0
	Commit	a9e40b0
	Direct Download	jetpack-prototype-build-pr18270-a9e40b0.apk

Note: Google Login is not supported on these builds.

[irfano]

Thank you for being patient with my review. 😄
Great job on the well-structured small PR!
I added some questions, concerns, and nitpicking suggestions. They are all ignorable, so I'm approving the PR but not merging it to give you the flexibility to address my comments.

[zwarm]

@irfano - Thanks so much for the review. I appreciate the time you took to provide the feedback; however I won't be making any changes directly to this PR since I'm already 4 branches ahead locally. I did jot down a few of your nitpicks to address in a future PR. 🙇